Every design that I do in photoshop that is destined for print should it be in CMYK color model ?

-I am creating a magazine cover for print in photoshop, so should I use always the CMYK color model for all the designs that i wanna print or I can use the RGB color model ? I am asking this because in order to get the colors that I want I should use the RGB color model ( colors more brighter than in CMYK) . so plz help me what should I do ?